Recently, the recording density of magnetic recording devices has rapidly increased, concurrently with an increase in the amount of information to be handled. Therefore, a magnetic head including a read element having a high sensitivity and a high reproducing output signal is now required. To meet this requirement, a magnetic head comprising a read element including a giant-magnetoresistive (GMR) film to provide a high reproducing output signal has been developed and further refined to present. Furthermore, research and development of a read element including, as a next-generation magnetoresistive film, a tunnel-magnetoresistive (TMR) film or a current-perpendicular-to-the-plane (CPP) GMR film, in which current flows through stacked surfaces of the GMR film, is underway in order to further increase sensitivity and reproducing output signal.
A read element including a TMR film or a CPP-GMR film has a structure different from that of a read element including a conventional GMR film. In the latter instance, the read element has a current-in-the-plane (CIP) structure, in which a sensing current flows in a direction in a plane of stacked surfaces of the GMR film, and electrodes for supplying the sensing current are provided on both sides of the GMR film. On the other hand, in the former instance, since the read element has a CPP structure, in which a sensing current flows in a direction perpendicular to a plane of stacked surfaces of the TMR film or the CPP-GMR film, electrodes for supplying the sensing current are stacked on the magnetoresistive film.
As described hereafter, the magnetic properties of a read element having a CPP structure may be significantly degraded during manufacture of a magnetic head including the read element. In such a read element having a CPP structure, a sensing current flows perpendicularly to stacked surfaces in a thickness direction of a magnetoresistive film between an upper magnetic shield, which may act as an upper electrode, and a lower magnetic shield, which may act as a lower electrode. Therefore, when a circuit in the read element having the CPP structure short-circuits between the upper magnetic shield and the lower magnetic shield, the circuit becomes a short circuit for the sensing current, leading to a reduction in the reproducing output signal of the read element.
The short circuit is formed on an end face at an air-bearing-surface side of the magnetoresistive film, when the magnetoresistive film is processed by mechanical polishing, leading to a reduction in the reproducing output signal of the read element. Several methods have been proposed for the purpose of hindering the formation of the short circuit, which degrades the original properties of the magnetoresistive film. Japanese Patent No. 3153167 discloses means for hindering the formation of such a short circuit by performing ion-beam irradiation after mechanical polishing.
However, even in instances where the formation of such a short circuit was hindered by ion-beam irradiation, a reduction in the resistance or the reproducing output signal of the read element nevertheless occurred. As a result, many conventional magnetic heads include a read element with a low signal-to-noise (S/N) ratio, which impedes the attainment of desired properties.